PARKLAND, Fla. – The school resource deputy at Marjory Stoneman Douglas High School waited outside the school building as the shooting unfolded last Wednesday. Scot Peterson, the deputy, never went in after taking a position on the west side of the building, Broward County Sheriff Scott Israel said in a news conference.

Peterson resigned on Thursday after he was suspended by Israel pending an internal investigation into his actions, Israel said.

Delayed surveillance footage

Surveillance footage from the Florida high school where 17 people were fatally shot and more than a dozen others wounded was not shown live, as responding officers initially thought.

According to Coral Springs Police Chief Tony Pustizzi, the footage had been rewound, and police were watching it on a 20-minute delay, leading them to believe the gunman, Nikolas Cruz, was still in the building when he was long gone.

“The delay never put us in a situation where any kids’ lives were in danger, any teachers lives were in danger,” Pustizzi said at a news conference Thursday afternoon.

When officers arrived on the scene of the shooting, he said, they wanted to gain access to the security footage to learn what happened and where the perpetrator could be.

But last Wednesday the footage was rewound, Pustizzi told reporters. At some point, there was a miscommunication and officers believed they were watching real-time footage.

“The issue was more of a communications failure on who was reviewing the tape, letting our guys know that it was a 20-minute delay in what they were reviewing,” Pustizzi said.

The rewound footage did not put any lives in danger, Pustizzi said, but it “did cause some confusion” when officers entered the school.

“At first the the guys are hearing, ‘Oh he’s on the second floor,'” Pustizzi said in the news conference. “Well it’s not true. Because we have people on the second floor, and the people are saying, ‘No, he’s not on the second floor.'”

The Broward County School district said in a statement that its security system footage could be reviewed in both real-time or be rewound to see events that were previously recorded.

“During the immediate response to the event, the system was being viewed in real-time and the recorded footage was being viewed to retrace the actions of the shooter,” the statement said, adding that the district no longer had access to the footage or the server it was stored on because investigating authorities have it.

‘I expected to be in a gunbattle’

The delay led police to brace for a shootout when the gunman was actually long gone, Coral Springs Police Capt. Brad McKeone said.

But McKeone, one of the responding officers, said the delay did not hinder access to the victims.

“It had no delay. It didn’t slow us down to getting us to anybody,” McKeone told CNN.

The main difference, he said, was that officers thought they were going to confront the gunman. In reality, the shooter had already left Marjory Stoneman Douglas High School in Parkland.

“I expected to be in a gunbattle,” McKeone said.

Broward County Public Schools had not responded to CNN’s request for comment Thursday about the school surveillance system. The Broward County Sheriff’s Office, which is leading the shooting investigation, also has not explained why the video was on tape delay.

Gunman was already at Walmart

While the rewound footage might not have increased the number of casualties, it did hamper efforts to locate the gunman.

McKeone said about 20 to 25 officers were on the first, second and third floors of the school when they thought the shooter was still inside.

“Somebody would say, ‘He’s on the second floor,’ and we had guys on the second floor saying, ‘We’re on the second floor, we don’t see him.’ That’s when we figured out there’s a tape delay,” Pustizzi told the Sun Sentinel.

According to police scanner traffic from the streaming website Broadcastify, at 2:43 p.m. on February 14, police found someone to give them access to the school’s security footage.

“I got a guy here outside the building that can get cameras,” says one voice. “We’re going to go inside and go get to the cameras.”

By 2:54 p.m., police were watching the gunman make his way through the building.

“They are monitoring the subject right now,” one person says. “He went from the third floor to the second floor. He may have a gas mask on now. Stand by for further. They’re monitoring him on camera.”

But the suspect had fled the building 26 minutes earlier at 2:28 p.m., according to a preliminary timeline provided by the Broward County Sheriff’s Office.

By 2:50 p.m., the suspect had already bought a drink at a Subway restaurant inside a Walmart store and left on foot, four minutes before scanner traffic said the gunman was still on the second floor of the school.

At 3:02 p.m., when the Broward County timeline says Cruz briefly stopped at a nearby McDonald’s, an officer says the suspect dropped a bag near a stairwell. Another officer asks if the footage is a recording.

“Yes, sir. It’s about a 20-minute delay,” the first officer says. “They’re following him on video on the camera. They had him exiting the building, running south.”